hush: cmd and arithmetic also need the fix for FILE rewind

Discovered by running testsuite with a newest glibc

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

shell/hush.c

@@ -1477,19 +1477,50 @@ static sighandler_t install_sighandler(int sig, sighandler_t handler)
 	return old_sa.sa_handler;
 }
 
+static void hush_exit(int exitcode) NORETURN;
+static void fflush_and__exit(void) NORETURN;
+static void restore_ttypgrp_and__exit(void) NORETURN;
+
+static void restore_ttypgrp_and__exit(void)
+{
+	/* xfunc has failed! die die die */
+	/* no EXIT traps, this is an escape hatch! */
+	G.exiting = 1;
+	hush_exit(xfunc_error_retval);
+}
+
+/* Needed only on some libc:
+ * It was observed that on exit(), fgetc'ed buffered data
+ * gets "unwound" via lseek(fd, -NUM, SEEK_CUR).
+ * With the net effect that even after fork(), not vfork(),
+ * exit() in NOEXECed applet in "sh SCRIPT":
+ *	noexec_applet_here
+ *	echo END_OF_SCRIPT
+ * lseeks fd in input FILE object from EOF to "e" in "echo END_OF_SCRIPT".
+ * This makes "echo END_OF_SCRIPT" executed twice.
+ * Similar problems can be seen with die_if_script() -> xfunc_die()
+ * and in `cmd` handling.
+ * If set as die_func(), this makes xfunc_die() exit via _exit(), not exit():
+ */
+static void fflush_and__exit(void)
+{
+	fflush_all();
+	_exit(xfunc_error_retval);
+}
+
 #if ENABLE_HUSH_JOB
 
-static void xfunc_has_died(void);
 /* After [v]fork, in child: do not restore tty pgrp on xfunc death */
-# define disable_restore_tty_pgrp_on_exit() (die_func = NULL)
+# define disable_restore_tty_pgrp_on_exit() (die_func = fflush_and__exit)
 /* After [v]fork, in parent: restore tty pgrp on xfunc death */
-# define enable_restore_tty_pgrp_on_exit()  (die_func = xfunc_has_died)
+# define enable_restore_tty_pgrp_on_exit()  (die_func = restore_ttypgrp_and__exit)
 
 /* Restores tty foreground process group, and exits.
  * May be called as signal handler for fatal signal
  * (will resend signal to itself, producing correct exit state)
  * or called directly with -EXITCODE.
- * We also call it if xfunc is exiting. */
+ * We also call it if xfunc is exiting.
+ */
 static void sigexit(int sig) NORETURN;
 static void sigexit(int sig)
 {
@@ -1544,7 +1575,6 @@ static sighandler_t pick_sighandler(unsigned sig)
 }
 
 /* Restores tty foreground process group, and exits. */
-static void hush_exit(int exitcode) NORETURN;
 static void hush_exit(int exitcode)
 {
 #if ENABLE_FEATURE_EDITING_SAVE_ON_EXIT
@@ -1588,15 +1618,6 @@ static void hush_exit(int exitcode)
 #endif
 }
 
-static void xfunc_has_died(void) NORETURN;
-static void xfunc_has_died(void)
-{
-	/* xfunc has failed! die die die */
-	/* no EXIT traps, this is an escape hatch! */
-	G.exiting = 1;
-	hush_exit(xfunc_error_retval);
-}
-
 
 //TODO: return a mask of ALL handled sigs?
 static int check_and_run_traps(void)
@@ -5913,7 +5934,8 @@ static FILE *generate_stream_from_string(const char *s, pid_t *pid_p)
 		) {
 			static const char *const argv[] = { NULL, NULL };
 			builtin_trap((char**)argv);
-			exit(0); /* not _exit() - we need to fflush */
+			fflush_all(); /* important */
+			_exit(0);
 		}
 # if BB_MMU
 		reset_traps_to_defaults();
@@ -6467,22 +6489,7 @@ static void dump_cmd_in_x_mode(char **argv)
  * Don't exit() here.  If you don't exec, use _exit instead.
  * The at_exit handlers apparently confuse the calling process,
  * in particular stdin handling. Not sure why? -- because of vfork! (vda)
- * Also, it was observed that on exit(), fgetc'ed buffered data
- * gets "unwound" by some libcs, via lseek(fd, -NUM, SEEK_CUR).
- * With the net effect that even after fork(), not vfork(),
- * exit() in NOEXECed applet in "sh SCRIPT":
- *	noexec_applet_here
- *	echo END_OF_SCRIPT
- * lseeks fd in input FILE object from EOF to "e" in "echo END_OF_SCRIPT".
- * This makes "echo END_OF_SCRIPT" executed twice. exexit() is the fix.
  */
-#if ENABLE_FEATURE_SH_STANDALONE
-static void exexit(void)
-{
-	fflush_all();
-	_exit(xfunc_error_retval);
-}
-#endif
 static void pseudo_exec_argv(nommu_save_t *nommu_save,
 		char **argv, int assignment_cnt,
 		char **argv_expanded) NORETURN;
@@ -6563,7 +6570,6 @@ static NOINLINE void pseudo_exec_argv(nommu_save_t *nommu_save,
 # if BB_MMU /* see above why on NOMMU it is not allowed */
 			if (APPLET_IS_NOEXEC(a)) {
 				debug_printf_exec("running applet '%s'\n", argv[0]);
-				die_func = exexit;
 				run_applet_no_and_exit(a, argv);
 			}
 # endif
@@ -7804,6 +7810,7 @@ int hush_main(int argc, char **argv)
 	INIT_G();
 	if (EXIT_SUCCESS != 0) /* if EXIT_SUCCESS == 0, it is already done */
 		G.last_exitcode = EXIT_SUCCESS;
+
 #if ENABLE_HUSH_FAST
 	G.count_SIGCHLD++; /* ensure it is != G.handled_SIGCHLD */
 #endif
@@ -7893,7 +7900,7 @@ int hush_main(int argc, char **argv)
 	/* Initialize some more globals to non-zero values */
 	cmdedit_update_prompt();
 
-	die_func = xfunc_has_died;
+	die_func = restore_ttypgrp_and__exit;
 
 	/* Shell is non-interactive at first. We need to call
 	 * install_special_sighandlers() if we are going to execute "sh <script>",